Method for manufacturing a block bag

ABSTRACT

A method for manufacturing a block bag of thermoplastic material with at least one filling valve from a tubular foil part having bottom flaps and at least one corner flap forming the valve being longer than the bottom flaps, wherein the bottom flaps are folded around a heat isolating piece and the stack of foils forming the bottom are heatsealed together by applying heat from both sides of the stack. The seals are obtained by spot welding, or formed as labyrinth seals. The end of the corner flap forming the valve may be stretched or subjected to a superficial incision, or creasing operation. By incision, or removing part of the corner flap forming the valve, a valve having a V form is obtained.

United States Patent de Vries 3,688,650 i451 Sept. 5, 1972 [54] METHODFOR MANUFACTURING A BLOCK BAG Jan Roelof Jochem de Vries, Hardenberg,Netherlands Assignee: lndustriele Ondememing Wavin N.V., Zwalle,Netherlands Filed: Aug. 26, 1969 Appl. No.: 853,624

Inventor:

US. Cl ..93/35 R, 93/8 VB, 229/62.5 Int. Cl. ..B3lb 49/04, 865d 31/14Field of Search.....93/8 VB, 35; 229/625; 150/9 References Cited UNITEDSTATES PATENTS 2/1966 Gennerich et al. ..229/62.5 3/1966 Lissner ..93/8X 2/1968 Shaw ..229/62.5 3/1969 Kasting et a1. ..229/62.5 X

Netherlands, ..6812161 FOREIGN PATENTS OR APPLICATIONS 961,222 6/1964Great Britain ..229/62.5

Primary Examiner-Theron E. Condon Assistant Examiner-Neil AbramsAttorney-Irving M. Weiner ABSTRACT A method for manufacturing a blockbag of thermoplastic material with at least one filling valve from atubular foil part having bottom flaps and at least one comer flapforming the valve being longer than the bottom flaps, wherein the bottomflaps are folded around a heat isolating piece and the stack of foilsforming the bottom are heatsealed together by applying heat from bothsides of the stack.

The seals are obtained by spot welding, or formed as labyrinth seals.The end of the comer flap forming the valve may be stretched orsubjected to a superficial incision, or creasing operation.

By incision, or removing-part of the corner flap forming the valve, avalve having a V form is obtained.

3 Claims, 13 Drawing Figures P'A'IENIEDsEP '91: 3,688,650

' sum a nr 6 I METHOD FOR MANUFACTURING A BLOCK BAGv The inventionrelates to a method for manufacturing a block bag with at least onefilling valve. By making two longitudinal incisions from one end of apart of a thermoplastic tubular foil thus forming two corner flaps andtwo bottom flaps, folding inwards said corner flaps about diagonal linesextending between the end point of the incision and a point on thelongitudinal edge of the tubular foil, folding the bottom flaps about across folding line, inserting a separating means, clamping said comerflaps and bottom flaps on each other and activating a sealing membersuch that longitudinal bottom seals and transverse bottom seals areproduced by heatsealing together said two bottom flaps and one of saidcorner flaps with said bottom flaps.

Such a method is known, but the plastic bags obtained thereby do notmeet the requirements, especially as far as the properties of quality ofthe sealed bottom and the closure are concerned. Moreover difficultiesare often experienced on filling such bags by means of bag fillingmachines.

It is now an object of the invention to provide va method formanufacturing an improved bag.

Such a method is characterized according to the invention in that thestarting point is a part of a thermoplastic tubular foil. At least onecorner flap, constituting the valve, is longer in the longitudinaldirection of the tubular foil than the bottom flaps. After the cornerflaps have been folded inwards the bottom flaps are folded about a crossfolding line extending substantially perpendicular to the longitudinalaxis of the part of the tubular foil in the portion of the non-incisedtubular foil part following after the point of inci- 51011.

By starting from a part of a tubular foil at least one of the cornerflaps of which is longer, in the' longitudinal direction of the tubularfoil, than the bottom flaps and folding about a folding line of thebottom flap, which is situated in the portion of the non-incised tubularfoil part following after the end points of the incision, it is possibleto obtain a very efficiently constructed bag which can be heatsealed ina minimum of operations, and which furthermore is very solid. Thissolidity results from the fact that, almost exclusively, a peeling loadis applied to the seals on filling such bags. Y

In order to reduce to a minimum the process of welding the layers in thebottom on each other a triangular portion is removed from the tubularfoil part at the end thereof and at the location of the line of incisionbetween a bottom flap and a corner flap, preferably whilst formingslanting corner flap edges along the line of incision.

According to a very preferred embodiment said seals are producted byapplying heat to the foil layers to be heatsealed from both sides of thesuperposed foil layers, that is from the side of the separating meansand from the sealing member.

The invention is hereinafter clarified with reference to the drawingrepresenting an embodiment for manufacturing a plastic bag according tothe invention, various details of the invention being disclosed in thecourse of the description.

In the drawing:

FIG. 1 is a flattened part of a tubular foil used for manufacturing abag;

FIG. 2 shows a perspective view of such a tubular foil P FIG. 3represents a tubular foil p'art after the corner flaps have beenunfolded;

.FIG. 4 represents an unfolded tubular foil part before introducing aseparating means connected with a sealing member;

FIG. 5 shows a separating means with heatable parts disposed in thebottom portion of the bag;

FIG. 6 represents a bottom portion of the bag after the sealing membertogether with the separating means is disposed on the bottom to beformed;

FIG. 7 is a sealed bottom with bag, obtained according to the method ofthe invention;

FIG. 8 shows one embodiment of a pattern for cutting foil parts from atubular foil;

FIG. 9 shows a preferred embodiment of a foil part out from a tubularfoil utilizing the pattern shown in FIG. 8;

FIG. 10 is a flattened part of a tubular foil having two comerflaps ofequal length; v

FIG. 11 shows a perspective view of the tubular foil parts of FIG. 10;

FIG. 12 represents the tubular foil part of FIG. 10

and 1 1 after the corner flaps have-been unfolded;

FIG. 13 represents a completely unfolded tubular part before introducinga-separating means.-

The FIGS. 1 and 2 represent a tubular foil part denoted by l which isprovided with two longitudinal incisions 2 forming two comerflaps, afirst cornerflap 5 and a second or other corner flap 5, and two bottomflaps 6 and 6. The first comer flap 5 is longer, in the longitudinaldirection of the tubular foil, than the bottom flaps 6, 6', while theother corner flap 5' is shorter, in the longitudinal direction, than thebottom flap 6. The bottom flaps 6,6 are provided with end edges 8 and8'. The corner flaps 5, 5' are inwards folded about the diagonal lines3, 3' (see FIG. 3) according to the arrows 9, 9' as represented in FIG.2. These diagonal lines extend between the points 7, 7' of incision 2,2' and the point of intersection of the folding lines 3, 3' with thelongitudinal edges of the foil part.

Before folding according to the diagonal lines a triangular portion isremoved from the corner flaps 5, 5 at the end of the tubular foil partwhereby the slanting edges 10, 10' are obtained.

' After folding the corner flaps 5, 5' about the diagonal lines 3, 3'whereby the angular points ll, 11' are obtained, which can beinterconnected by the connecting line 12, a separating means in theshape of a heat isolating piece or stamping piece 13, is introduced insuch a way that the stamping piece 13 comes to lie over the corner flap5, and the comer flap 5' is situated over the stamping piece 13. Thestamping piece 13 is hinged to the heatable sealing member 14.Preferably the stamping piece 13 which is going to cooperate with theheated sealing member 14 is provided with sealing bars or wires 13a.

Hereupon the bottom flaps 6, 6' are folded, according to the arrow 9a,about the cross folding line 15, 15' which is situated in the tube foilpart behind the points 7, 7 of incision 2, 2'. Preferably theperpendicular distance IIb between the transverse folding lines 15, 15'and the end edges 8, 8' of the bottom flaps 6, 6' is almost equal to,but preferably slightly smaller than twice the distance b between thetransverse folding lines 15, 15 andthe connecting line 12 between theangular points 11, ll.

Thereupon the sealing member 14 provided with sealing bars or wires 14astamp hingedly connected with the is pressed on the folded and unfoldedbottom corner flaps. It should be noted that just before heatsealing iseffected the sealing bars or wires 13a and 14a lie opposite each other.By pplying heat the longitudinal and cross sealings 17 are formed.

It is advisable to provide partial diagonal seals 18. These seals aswell as the seals 16 and 17 can be efficiently formed by spot welding,whereby the air in the bag can easily escape on filling. This can beobtained by using sealing bars or wires having profiles providing spotseals.

The longitudinal seals 16 and the diagonal seals 18 and the cross seals17 are advantageously formed as labyrinth seals. in this way the blockbag obtained according to the invention is specially suitable to let theair escape on'filling the bag without solid substances being takenalong.

Due to the suitable selection of the distance llb between the end edges8, 8 and the cross folding line l5, 15', that is slightly smaller thantwice the distance between the cross folding line 15, 15' and theconnecting line 12 between the angular points 11, 11', a proper closurecan be achieved by means of a rectangular welded joint. In order to fixinternal tubular foil parts in position in the best possible way anothercross seal 17 is formed across the two edges 8, 8' of bottom flap 6, 6at one end of the folded bottom flaps and in addition thereto one ormore diagonal seals 18.

As has been stated hereinbefore it is advisable to bevel the cornerflaps 5, in such a way that the slanting edges 10, are obtained. Thisconstruction is advantageous in that less layers of material need besealed locally to each other.

The tubular foil part 1 is obtained by cutting along cutting lines 4, 4'in, and removing triangular areas 20, 20' from -a tubular foil 19. Thiscutting process may be accomplished with a single cutter member having acial incisions in the surface of the foil of the flap. In adcutter.

cutting surface corresponding to this configuration in one operation.

By this process of cutting tubular foil parts 1 are obtained, the cornerflaps 5 of which are diagonally oppositely situated.

If a rather thick material is used for the tubular foil, the corner flap5 consituting a valve of the bag is relatively stiff and inflexible, andwill not conform to the bottom of the closure of the bag. Thisdifiiculty can be overcome by decreasing the thickness of the cornerflap 5 by subjecting its to a transverse stretching operation. Thisstretching operation decreases the thickness of the corner flap 5, andincreases its surface area. As a consequence, the flap 5 adapts itselfmore readily to the shape of the closure of the bag. After the bag isfilled and turned upside down, the filling material in the bag pressesagainst the portion of the flap 5 situated within the bag. Due to theincreased surface area of the flap 5, small channels are formed betweenthe flap 5 and the other components comprising the closure of the bagthrough which air can escape from the closed bag.

In the alternative, an increased flexibility of the corner flap 5 orvalve can also be achieved without increasing its surface area byemploying lines of weakness 21. These lines of weakness comprise verysuperfi- The FIGS. 10 and 11 represent a tubular foil part denoted by 31which is provided with two longitudinal incisions 32 while forming twocomer flaps 35 and 35' and two bottom flaps 36 and 36'.

. A portion 34, 34' is severed from these bottom flaps 36 and 36 wherebythe end edges 38, and 38' of the bottom flaps 36 and 36' are formed. Thetwo corner flaps 35 and 35' now of equal length are inwards folded aboutdiagonal lines 33 and 33' according to the arrows 39 and 39', asrepresented in FIG. 3. These diagonal lines extend between the, endpoints of the incisions 37 and 37' and the folding lines 39, 39'.

For. the purpose of folding, and to require fewer layers of materialwhich need be sealed locally to each other, a part of the comer flaps35, 35 is removed, whereby the oblique edges 40 and 40 are obtained.

In some cases the long valve being formed by corner flap 35 causesdifficulties in filling machines for hard materials. in order to meetthis difficulty an incision may be given in the longitudinal edge 43 ofcorner flap 35 from the free end.

More preferably a triangular part 44, 44 is removed from the end of thecomer flap 35 constituting the valve whereby the cutting edges 46, 46'are formed. The length'of the longitudinal edge 43 of the tubular foilremoved from the corner flap 35 is less than thevertical distancebetween the free ends'38, 38' of the bottom flap 36, 36' and the freeend of corner flap 35. In this way the valve part has a V-form so thateven with short filling pipes of filling machines the valve does notcome into contact with the filling material coming from the filler pipe,thus preventing the valve or flap 35 from interfering with the flow offilling material and deflecting it away from the valve.

After folding the comer flaps about the lines 33, 33 whereby the angularpoints 41, 41' are obtained, between which extends a connecting line 42,a separating means in the shape of a stamping piece 13 is introduced,the stamping piece 13 being introduced in such a way that the comerflaps 35' comes to lie over the stamping piece 13 and the comer flaps 35comes to lie under the stamping piece 13. The stamping piece 13 ishingedly connected with the sealing member 14, both being provided withsealing bars or wires 13d and 14a as already discussed.

Hereupon the bottom flaps are folded about a cross folding line 45, 45which is situated in such a way in the tube foil part behind the endpoints 37, 37' of the incisions, that the perpendicular distance Ilabetween the cross folding line 45, 45 and the end edges 38, 38' of thebottom flaps 36, 36' is slightly smaller than twice the distance abetween the transverse folding line 45, 45' and the connecting line 42between the angular points 41,41.

Thereupon the sealing member 14 hingedly connected with the stampingpiece 13 is pressed on the folded bottom flaps, whereby longitudinalseals and transverse seals corresponding to seals 16 and 17 of FIG. 7are obtained.

It is advisable to provide partdiagonal seals corresponding to seals 18.Of course these seals can also be very efiiciently formed by spotweldingwhereby the air in the bag can easily escape on filling.

These longitudinal seals 16 may also, together with diagonal seals 18and transverse seals (corresponding to seals 16, 18 and 17) be formed aslabyrinth seals.

Due to the suitable selection of the distance Ila between the end edges38, 38' and the transverse folding line 45, 45' and the connecting line42 a rectangular welded joint suffices for a good closure. In order tofix in position the loose hanging tubular foil parts in the bestpossible way another transverse seal is provided between the'twotransverse seals at the ends and in addition thereto the diagonal seals.

The good quality of the seals appears from the fact that the shearingstrength of the welded joint is 6.3 kg] 1 mm, which is to 20 percentmore than normal. It should'be noted in this connection that the tensilestrength of the tubular foil materials is 6.3 to 6.5 kg per cm2.

The aforementioned method is of special importance for the manufactureof bags from polyethylene, a rather stiff material in working up.

The tubular foil material is always a thermoplastic material such aspolyvinylchloride or polyethylene, preferably the bags are manufacturedfrom polyethylene material. It will be obvious that other thermoplasticmaterials can also be used for manufacturing the described thermoplasticblock bags.

What I claim is:

l. A method of manufacturing a block bag from a thermo plastic tubularfoil material having at least one disposed between said first and secondcorner flaps;

folding each of said first and second corner flaps inwardly about adiagonal folding line defined by said second point of said incisionnearest it, and a third point on an adjacent longitudinal edge of saidtubular foil spaced longitudinally from said transverse end edge of saidtubular foil more distant than said second point;

inserting a separating member with sealing bars under said second cornerflap and over said first comer flap;

folding said bottom flaps inwardly about a folding line transverse tosaid longitudinal axis, said transverse folding line situated between aline defined by said third points on said longitudinal edges of saidtubular foil, and a line defined by said second points of saidincisions, in an overlapping relationpl i g a sealing member withsealingbars over a closure formed by said bottom flaps and said comer flaps;

activating said seaiing bars from both sides of said closure formedbyfolding said first and second corner flaps and said bottom flap to sealsaid bottom flaps, and said comer flaps together; and

removing said separating member after sealing said closure from bothsides.

2. A method of manufacturing block bags substantially as set forth inclaim 1 further characterized by:

stretching said first comer flap constituting a valve in a directiontransverse to said longitudinal axis of said tubular foil to make saidflap thinner and more flexible to more readily adapt to theconfiguration of said closure and to form channels through which trappedair may escape.

3. A method of manufacturing block bags substantially as set forth inclaim 1, further characterized by:

forming superficial fourth incisions in said first corner flapconstituting a valve in a direction substantially parallel to saidlongitudinal axis of said tubular foil to make said flap more flexibleand more readily adaptable to the configuration of said closure and toform channels through which trappedairmay escape.

1. A method of manufacturing a block bag from a thermo plastic tubularfoil material having at least one filling valve, which comprises thesteps of: making parallel spaced apart first and second incisions insaid tubular foil parallel to a longitudinal axis of said tubular foil,each defined by a first point on a transverse end edge of said tubularfoil and a second point on said tubular foil spaced longitudinally fromsaid first point, thus forming a first corner flap constituting a valve,a second corner flap, and two bottom flaps, said bottom flaps beingdisposed between said first and second corner flaps; folding each ofsaid first and second corner flaps inwardly about a diagonal foldingline defined by said second point of said incision nearest it, and athird point on an adjacent longitudinal edge of said tubular foil spacedlongitudinally from said transverse end edge of said tubular foil moredistant than said second point; inserting a separating member withsealing bars under said second corner flap and over said first cornerflap; folding said bottom flaps inwardly about a folding line transverseto said longitudinal axis, said transverse folding line situated betweena line defined by said third points on said longitudinal edges of saidtubular foil, and a line defined by said second points of saidincisions, in an overlapping relationship; placing a sealing member withsealing bars over a closure formed by said bottom flaps and said cornerflaps; activating said sealing bars from both sides of said closureformed by folding said first and second corner flaps and said bottomflap to seal said bottom flaps, and said corner flaps together; andremoving said separating member after sealing said closure from bothsides.
 2. A method of manufacturing block bags substantially as setforth in claim 1, further characterized by: stretching said first cornerflap constituting a valve in a direction transverse to said longitudinalaxis of said tubular foil to make said flap thinner and more flexible tomore readily adapt to the configuration of said closure and to formchannels through which trapped air may escape.
 3. A method ofmanufacturing block bags substantially as set forth in claim 1, furthercharacterized by: forming superficial fourth incisions in said firstcorner flap constituting a valve in a direction substantially parallelto said longitudinal axis of said tubular foil to make said flap moreflexible and more readily adaptable to the configuration of said closureand to form channels through which trapped air may escape.